Mill hole chutes are used in mining operations to provide stable walls for mine passages in which ore, rock and other materials may be hauled. Chutes with steel-plate lined structures have been proposed.
Mill hole liner rings usually comprise a plurality of steel plates welded or otherwise connected together to form a short cylinder. Each cylinder is then welded or otherwise connected successively to another cylinder to form a mill hole chute.
There are many types of connectors which have been devised for assembling liner rings to form mill hole chutes.
A disadvantage of many connector assemblies of the prior art which are used in mill hole chutes is that they are very labour intensive and time-consuming. This results in high labour costs. Furthermore, the assembly of some of the prior art chutes requires special training and equipment. For example: Canadian Patent 788,806 entitled Angle Lug Chute shows a connector comprised of flanges with apertures for receiving a bolt which is then held in place with a nut; Canadian Patents 630,028 and 709,229 describe a steel mill hole form in which rods are inserted through several tubular members which are located on adjacent mill hole liner rings and segments and wherein the rods are then secured in place by a wedge means.
The prior art devices of Canadian Patents 788,806, 630,028, and 709,229 require very precise manufacture of the cylinder segments failing which the bolts or rods cannot be inserted through the apertures or tubular members of abutting cylinders. Even with precise manufacture of the cylinders, residual stresses from the manufacturing process or from transportation and handling can result in misalignment of the apertures. Misalignment results in increased time and labour costs being incurred as the segments and cylinders must be aligned using bars, clamps or pullers. Such alignment methods are particularly difficult when the mill hole chute is being assembled in the typically cramped quarters encountered in underground installations.
In U.S. Pat. No. Re. 21,101 a connector for a welding apparatus is described. The connector is comprised of a rectangular plate containing two apertures thereon. When the rectangular plate is placed over a first and second holding lug, wherein each holding lug is intimately attached to a first and second metal sheet, respectively, the metal sheets are held together. Each holding lug contains an aperture in which wedge means may then be inserted to lock the plates together. A further wedge means is described to align the plates more precisely.
U.S. Pat. No. Re 21,101 describes a three member (rectangular plate and two holding lugs) connector assembly with wedge means. The present invention is a two member (a first and second connector elements) connector assembly with wedge means. Therefore, the applicant's invention requires less components for a less complicated system.
U.S. Pat. No. Re. 21,101 describes a complicated connector system for aligning metal sheets temporarily in order to enable abutting edges to be welded together. The holding lugs must be permanently attached to the sheet metal at very precise distances in two directions. The rectangular plate in U.S. Pat. No. Re. 21,101 cannot be used to hold the metal sheets together if the holding lugs are not precisely mounted. To overcome the precision required in mounting the holding lugs, the apertures on the rectangular plate are made large enough to allow for the deviations in the location of the holding lugs so that a further wedge means must be used to lock the rectangular plate and hence plate members together.
The present invention requires that the connector clip and connector tongue of the connector assembly be precisely orientated and mounted in one direction only since they are located on the rim of each plate member. The location of the connector clip and connector tongue on the rim of the face of each plate member also allows for easier alignment of the two plate members than U.S. Pat. No. Re. 21,101 discloses.
Many of the connector assemblies which have been proposed for mill hole liner chutes have not overcome the problem of poor alignment between adjacent plates. Poor alignment results in loose seams which can contribute to an unstable structure.